Blender is not rendering the camera view
Check also if you have a video in the Video Sequence Editor (VSE) that may block rendering the 3D view. You can swtich what to render (Compositor and/or Sequencer):


go to Properties Panel > Render 
than Section “Post Processing”: 
if you have checked [x] Sequencer and have clips or media in the VSE, than the 3D view will not render but the VSE instead, i.e. the “Sequencer”. So in that case un-check it for the Sequencer